About BS 546
Until the late 1950s residences in the UK, Ireland and many parts of the Commonwealth were provided with plugs and sockets defined by the British Standard No. 546. Because of a change in wiring of domestic electrical systems - from radial to ring circuits - BS 546 (round pins) was replaced by BS 1363 (fused plugs with rectangular pins). See the domestic wiring techniques page for details about radial and ring circuits.
The history of BS 546 can be traced back to BS 317, published in 1928. Its official title was "Hand-Shield and Side Entry Pattern Three-Pin Wall Plugs and Sockets". BS 317 was in 1930 replaced - with only minor alteration - by BS 372 Part II, which specified 2A, 5A, 15A and 30A plugs and sockets. BS 372 was superseded in April 1934 by BS 546 which included the same four plug/socket sizes with the same dimensions. Appendix A of BS 546-1934 allows for the optional inclusion of fuses up to 5A in any version, except the 2A plug, limited to 2A. The current version is BS 546-1950 (with various more recent amendments). Information provided by David Peacock IEng FIET.
The BS 546 15A variant is still applied in the UK in situations where sockets and plugs are build-in and/or a part of complex circuits (for example in theater wiring), in which it is difficult to trace a blown plug-fuse (BS 1363 plugs always have a fuse). Occasionally 5A devices are still used in the UK for centrally switched domestic lighting circuits, in order to distinguish them from normal power circuits.
The 30A variant was used for (semi-) industrial equipment. It is now replaced by high current and multiphase sockets and plugs defined by the IEC 60309 standard
Plugs and sockets that are essentially identical to BS 546
Image nos. 8 - 13 show sockets and plugs, made in India according to IS 1293 standard. The devices are bought in Bhutan that, like Nepal, has adopted the Indian standard. Images 14 and 15 show South African SANS 164 plugs, also based on BS 546.
8-9: Two types of Indian sockets that can be used for either 16A or 6A plugs (see image nos. 10 an 11) . Although fully comparable to BS 546, Indian IS 1293 plugs and sockets are rated at 240V - 16A or 6A, rather than 15A and 5A. Both types of sockets have safety shutters. Socket no. 9 has also a fuse and control light. The fuse is not hard wired; it is up to the electrician when installing the socket to wire the fuse (or not). Switch and fuse are not compulsary.
10: Indian 6A - 240V socket that can be used for earthed 6A plugs (3-pin, see no. 12) or non-earthed 6A plugs (2-pin, see no. 13). Brand name: Anchor. The spacing between L and N pins of earthed and non-earthed plugs differ. This is intrinsic to all BS 546 based plugs (see South African gallery for data).
11-12: IS 1293 16A plug (no. 11), and 6A (no. 12) plugs. The green arrows indicate the spacing between line (left) and neutral (right) pin. Also 3-pin IS 1293 plugs have an inspection hole to check earth pin wiring (see insets; compare with no.7)
13: Non-earthed 6A plug. This 2-pin plug is similar to the BS 4573 shaver plug, but lacks the partial insulation of the pins.
14: IS 1293 6A adapter plug for one earthed plug (as no. 12) and two not earthed plugs (as no. 13)
Manufacturers: Anchor Electricals PVT.LTD , India (nos. 8, 10-14) and CPL Pigmy, India (no. 9)
15-16: South African plugs according to SANS* 164 specifications. No. 15 is an example of SANS 164-1, rated at 16A-250V, while no.16 shows a 6A SANS 164-3 plug. Two aspects differ from BS 546 plugs used in the U.K.: (i) partial insulation of power pins is not compulsory and (ii) plug housing do not have an inspection hole for earth pin wiring. Manufacturers: no. 14: Litemaster (part of Crabtree, South Africa) and no. 16: Procast Manufacturing, South Africa.
More material is displayed in the South Africa gallery. * SANS stands for South African National Standard.
17: SANS 164-1, 16A-250V plug with a partly transparant housing. Manufacturer: Lumex (Lumex Clipsal Pty, now Schneider Electric).
More BS 546 plugs, adapters and multi-plugs
18: Plug of a power cord meant for double insulated appliances. The plug has a non-conductive 'earth' pin, which is needed to open the safety shutters and to enforce the correct orientation of line and neutral pin. The official name of a non-conductive pin is an Insulated Shutter Opening Device (ISOD).
19: 15A, 2-way converter plug (the second, top side set of slots is not visible), which allows the use of BS 1363 plugs in a house equipped with BS 546 sockets. According to BS 1363 standards converter plugs are provided with 13A fuse. Manufacturer: Voltex, South Africa.
20: BS 546 2A, 3-way multi-plug. Manufacturer: Clang.
Fused BS 546 plugs
In contrast to BS 1363 (see above comments) by far the most BS 546 plugs do not have a fuse. However, fused BS 546 plugs are offered as an extra means of protection.
21-22: 5A BS 546 plug with a 5A fuse. Note that fused BS 546 plugs have a rectangular shape, in contrast to the triangular, non-fused counterparts (see nos. 4 and 5). Brand name: MK Electric, England.
23-24: Fused 15A BS 546 safety adapter meant for a 15A and 5A BS 546 plug. Both outlets have safety shutters. It is indicated that the total loading must not exceed 15 Amps. The fitted 5A fuse only protects the 5A outlet. Brand name: MK Electric.
Both plugs have a small type of cartridge fuse (BS 646), rather than the larger BS 1362 fuses that are used in BS 1363 plugs.
Obsolete adaptable 2A, 5A, 15A two and three round pin plug.
Click here for Crater.
Classic BS 546
Old plugs and outlets made in Britain and China.
Click here for examples.
BS 372 : 1930 Part 1
Non-earthed plugs and sockets, and historical notes.
Click here for examples.
BS 52 : 1963
Bayonet cap (B22d-2) lamp holders with BS 52 plug adapter.
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